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Re: [PATCH RFC V2 1/1] x86, perf: Add a freq pmu driver

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  Re: [PATCH RFC V2 1/1] x86, perf: Add a freq pmu driver Andy Lutomirski <luto@amacapital.net> - 2015-07-21 08:10 +0200
    Re: [PATCH RFC V2 1/1] x86, perf: Add a freq pmu driver Stephane Eranian <eranian@google.com> - 2015-07-21 08:30 +0200
      Re: [PATCH RFC V2 1/1] x86, perf: Add a freq pmu driver Andy Lutomirski <luto@amacapital.net> - 2015-07-21 08:30 +0200

#1188687 — Re: [PATCH RFC V2 1/1] x86, perf: Add a freq pmu driver

On Mon, Jul 20, 2015 at 8:10 PM, Stephane Eranian <eranian@google.com> wrote:
> On Mon, Jul 20, 2015 at 8:49 AM, Kan Liang <kan.liang@intel.com> wrote:
>> From: Andy Lutomirski <luto@kernel.org>
>>
>> This patch adds freq PMU to support time and freq related counters
>> includes TSC, IA32_APERF, IA32_MPERF and IA32_PPERF.
>>
>> The events are exposed in sysfs for use by perf stat and other tools.
>> The files are under /sys/devices/freq/events/
>>
>> These events only support system-wide mode counting.
>>
>> The PMU type (attr->type) is PERF_TYPE_FREQ.
>>
>> Example:
>>
>> To caculate the CPU%
>> CPU_Utilization = CPU_CLK_UNHALTED.REF_TSC / TSC
>>
>> $ perf stat -e '{ref-cycles,freq/tsc/}' -C0 -- taskset -c 0 sleep 1
>> 3164023,,ref-cycles,1048387386,100.00
>> 2410812089,,freq/tsc/,1050022373,100.00
>> The CPU% for sleep is 0.13%.
>>
> This event is system-wide only. Thus, the kernel should return
> an error when you try to use it in per-thread mode. That would
> be more consistent with RAPL and uncore events.

I don't know enough about perf's inner workings to be sure, but can't
perf context switch free-running counters like this?

--Andy
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#1188693

On Mon, Jul 20, 2015 at 11:01 PM, Andy Lutomirski <luto@amacapital.net> wrote:
> On Mon, Jul 20, 2015 at 8:10 PM, Stephane Eranian <eranian@google.com> wrote:
>> On Mon, Jul 20, 2015 at 8:49 AM, Kan Liang <kan.liang@intel.com> wrote:
>>> From: Andy Lutomirski <luto@kernel.org>
>>>
>>> This patch adds freq PMU to support time and freq related counters
>>> includes TSC, IA32_APERF, IA32_MPERF and IA32_PPERF.
>>>
>>> The events are exposed in sysfs for use by perf stat and other tools.
>>> The files are under /sys/devices/freq/events/
>>>
>>> These events only support system-wide mode counting.
>>>
>>> The PMU type (attr->type) is PERF_TYPE_FREQ.
>>>
>>> Example:
>>>
>>> To caculate the CPU%
>>> CPU_Utilization = CPU_CLK_UNHALTED.REF_TSC / TSC
>>>
>>> $ perf stat -e '{ref-cycles,freq/tsc/}' -C0 -- taskset -c 0 sleep 1
>>> 3164023,,ref-cycles,1048387386,100.00
>>> 2410812089,,freq/tsc/,1050022373,100.00
>>> The CPU% for sleep is 0.13%.
>>>
>> This event is system-wide only. Thus, the kernel should return
>> an error when you try to use it in per-thread mode. That would
>> be more consistent with RAPL and uncore events.
>
> I don't know enough about perf's inner workings to be sure, but can't
> perf context switch free-running counters like this?
>
It should be able to but your patch does not seem to do this. I get zero
count when I try.
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#1188694

On Mon, Jul 20, 2015 at 11:21 PM, Stephane Eranian <eranian@google.com> wrote:
> On Mon, Jul 20, 2015 at 11:01 PM, Andy Lutomirski <luto@amacapital.net> wrote:
>> On Mon, Jul 20, 2015 at 8:10 PM, Stephane Eranian <eranian@google.com> wrote:
>>> On Mon, Jul 20, 2015 at 8:49 AM, Kan Liang <kan.liang@intel.com> wrote:
>>>> From: Andy Lutomirski <luto@kernel.org>
>>>>
>>>> This patch adds freq PMU to support time and freq related counters
>>>> includes TSC, IA32_APERF, IA32_MPERF and IA32_PPERF.
>>>>
>>>> The events are exposed in sysfs for use by perf stat and other tools.
>>>> The files are under /sys/devices/freq/events/
>>>>
>>>> These events only support system-wide mode counting.
>>>>
>>>> The PMU type (attr->type) is PERF_TYPE_FREQ.
>>>>
>>>> Example:
>>>>
>>>> To caculate the CPU%
>>>> CPU_Utilization = CPU_CLK_UNHALTED.REF_TSC / TSC
>>>>
>>>> $ perf stat -e '{ref-cycles,freq/tsc/}' -C0 -- taskset -c 0 sleep 1
>>>> 3164023,,ref-cycles,1048387386,100.00
>>>> 2410812089,,freq/tsc/,1050022373,100.00
>>>> The CPU% for sleep is 0.13%.
>>>>
>>> This event is system-wide only. Thus, the kernel should return
>>> an error when you try to use it in per-thread mode. That would
>>> be more consistent with RAPL and uncore events.
>>
>> I don't know enough about perf's inner workings to be sure, but can't
>> perf context switch free-running counters like this?
>>
> It should be able to but your patch does not seem to do this. I get zero
> count when I try.

Peter, help?  I'm guessing the fix is a line of two of code, but I
have no idea what line or two.

--Andy


-- 
Andy Lutomirski
AMA Capital Management, LLC
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